Primary myelofibrosis (PMF), essential thrombocythemia (ET) and polycythemia vera (PV) are monoclonal hematological disorders that belong to the classical BCR-ABL negative myeloproliferative neoplasms (MPN) (Campbell & Green, 2006). Since the 2005 discovery of a somatic mutation in the JAK2 kinase gene, a tremendous progress has been made in molecular diagnosis, clinical management, treatment and molecular understanding of MPN. The valine to phenylalanine (V617F) mutation constitutively activates the Jak2 kinase resulting in increased phosphorylation of its substrates (Stat5, Stat3, Erk, etc.) and leading to increased cytokine responsiveness of myeloid cells (Baxter et al, 2005; James et al, 2005; Kralovics et al, 2005; Levine et al, 2005). Identification of additional mutations soon followed such as in JAK2 exon 12 in PV (Scott et al, 2007) and in the thrombopoietin receptor gene MPL in PMF and ET (Pardanani et al, 2006; Pikman et al, 2006). Although the three MPN disease entities differ in their clinical presentation, they share many molecular as well as clinical features. The JAK2-V617F mutation is present in about 95% of PV cases, 60% PMF and 50% of ET cases, respectively. Mutations in JAK2 exon 12 are specific to about 3% of PV cases whereas MPL mutations are restricted to the PMF (5%) and ET (3%). All three MPN entities are predisposed at a variable degree to thrombosis, bleeding and leukemic transformation (Sverdlow et al, 2008). Although patients may remain in the chronic phase of MPN for several years, disease progression occurs in a form of secondary myelofibrosis in PV and ET, development of accelerated phase with variable degree of pancytopenia followed by leukemic transformation affecting all three MPN entities (Sverdlow et al, 2008).
Somatic mutations accumulate during the entire clonal evolution of MPN hematopoietic stem cells. These acquired genetic alterations may be point mutations, chromosomal lesions and epigenetic defects and they all may contribute to the fitness of the evolving clone (Klampfl et al, 2011; Kralovics, 2008). These mutations may accelerate proliferation by various means, decrease differentiation potential of progenitors or render them less susceptible to apoptosis. Mutations affecting these mechanisms have been described in genes such as TET2 (Delhommeau et al, 2009), EZH2 (Ernst et al, 2010), DNMT3A (Stegelmann et al, 2011), ASXL1 (Stein et al, 2011), and TP53 (Harutyunyan et al, 2011) in different types of myeloid malignancies including MPN (Milosevic & Kralovics, 2013). However, so far only JAK2 and MPL mutations are considered strongly MPN associated and they represent the most useful molecular markers of MPN.
Despite the progress made in the understanding of the molecular pathogenesis of MPN approximately half of the patients with PMF and ET lack a molecular marker for diagnosis as these patients are negative for both JAK2 and MPL mutations.
Thus, the technical problem underlying the present invention is the provision of means and methods for diagnosis of a myeloid malignancy.